The present invention relates to a self-supporting carcass for motor-vehicle tires, of the type comprising a pair of circumferentially inextensible anchoring rings or bead cores, each embedded in a bead defined along an inner circumferential edge of a tire. A pair of elastomeric fillers each of which extends along an outer circumferential edge of one of the anchoring rings, tapers radially away from the tire axis. A second carcass ply is superposed over a first carcass ply in a radially outer position, at least one of said carcass plies has its edges folded back around the bead cores and the elastomeric fillers. A tread band is disposed crown-wise to said carcass ply and a circumferentially inextensible belt structure extends as a ring, interposed between the carcass plies and the tread band. At least a pair of annular reinforcement inserts, made of elastomeric material of lenticular section, each of which is interposed between the first and second carcass plies, at a tire sidewall extends radially between one of the beads and the corresponding end of the belt structure.
The carcass in accordance with the invention is of the type used when it is desired that a tire have the capability of covering considerable distances at fair speed even in the case of complete deflation, for example as a result of a puncture.
It is known that there are different types of tires commonly referred to as "self-supporting tires" which have the quality of enabling a motor-vehicle to go on running at fair speed even when the tire has been accidentally deflated.
Among the different solutions suggested for the achievement of this particular feature it is particularly advantageous to adopt a carcass structure having reinforced sidewalls so that they can elastically withstand the load on the wheel when the sustaining action normally exerted by the air contained in the tire is no longer present. This solution has aroused great interest in the field, as it appears potentially capable of offering the self-support quality without impairing other characteristic performances of the tire too much, such as for example the direction steadiness, roadholding, side steadiness when turning and weaving and, also important, comfort during the ride.
It is apparent that this type of carcass, in order to be able to work in both situations, needs to be mounted on a rim of the type provided with suitable protuberances, commonly referred to as humps, ensuring the tire beads to be held on the wheel rim bead seats even in a situation of complete deflation.
The foregoing being stated, it is noted that the present carcass for self-supporting tires having reinforced sidewalls can be substantially classified in two different types.